Fire and water
The elements do not obviously assist each other. Fire wants to be seen and water wants to merge, so Leo's display meets a response that is sincere but hard to read, and Pisces's atmosphere meets a partner who prefers things stated.
What works is that Pisces is genuinely appreciative and Leo genuinely needs an audience that means it. What fails is that fire dries water out. Sustained proximity to Leo's certainty can leave Pisces with even less sense of its own outline than it started with. Leo rarely intends this and is usually the last to see it.
Fixed and mutable
Leo holds and Pisces adapts, and here the modalities do more damage than the elements. Pisces yields on almost everything, quickly and without comment, and Leo takes the absence of objection at face value.
The imbalance builds without either intending it. Eventually Pisces registers a large accumulated grievance that Leo has had no opportunity to address, and Leo, whose self-image depends on being generous, is genuinely wounded to hear it. The wound is real, and it does not change the fact that the account was accurate.
The Sun, Neptune and Jupiter
Leo belongs to the Sun, the only ruler that is also the chart's central body, which is a fair image of how the sign operates. Pisces goes to Neptune in modern practice and to Jupiter traditionally.
The Sun defines and Neptune dissolves, which is an unusually direct opposition of function. Jupiter behind Pisces is the friendlier link, since Jupiter and the Sun share a warmth and a generosity. Where those bodies actually sit is the useful question. A Leo with a water Moon reads Pisces far better than the sun signs would suggest.
Where it grinds
Directness. Leo says what it wants and expects the same in return. Pisces states preferences obliquely or not at all, and Leo, who is not a subtle reader, misses them repeatedly and is then accused of not noticing.
The second friction is over attention. Leo's need for it is open and Pisces's is not, so Pisces's needs go unserved by default rather than by refusal. That default is the thing to name early, because it does not correct itself.
Why the Suns do not decide it
A sun-sign pairing describes a tendency across a very large number of people. Two people are not a tendency, and nothing on a page like this can account for the particular history either of them brings.
The Moon shows what each needs at close quarters, Venus how warmth is expressed and received, Mars how conflict runs. Comparing those between two real charts is a different and far more specific exercise.
Questions people ask about this
What draws Leo and Pisces together?
Leo needs sincere appreciation and Pisces gives it without calculation. The attraction is real and does not settle the question of how the pairing runs.
What is the main imbalance?
Pisces concedes quietly and Leo reads quiet as agreement. Grievances accumulate unmentioned and arrive all at once.
Does the Sun and Neptune pairing matter?
They work in opposite directions, one defining and one dissolving. Jupiter, the traditional ruler of Pisces, is the warmer link between the two.
What is worth reading instead of sun signs?
Moon, Venus and Mars across both charts. Those are the placements that describe how two specific people actually get on.